1. Field of the Invention
The present invention relates to a process and an implementation device for adjusting the transmission and reception chains of the paths formed by a multipath transmission/reception device of a base station of a radiocommunications system, using in particular a multipath transmission/reception technique known by the abbreviation SDMA standing for "Space-Division Multiple Access".
2. Discussion of the Background
Systems for radiocommunication with mobiles are mostly based on the cellular network concept in which a base station communicates with a number of mobiles within the cell for which it is responsible.
For transmitting and receiving signals, base stations currently use only simple antenna systems, either of the single-sensor or multi-sensor type, with RF combination to ensure complete coverage, or else of the two-sensor type with selection to obtain space diversity in reception.
The concept of SDMA, now widely reported in the literature, is aimed at increasing the capacity of a base station by performing multipath transmission and reception in an adaptive and intelligent manner.
However, the setting up of this technique runs up against problems of implementation and of control of the distortions in the transmission and reception chains. In particular, the most disturbing phenomenon is the phase and amplitude dematching of the paths. During reception, this phenomenon will prevent a correct location fix on the mobile and hence the allocation of an SDMA frequency. During transmission, this problem may cause the transmission of a signal in an undesired direction.
The techniques for alleviating these problems are well known in respect of reception, since they are implemented in radio direction finders and consist in performing a calibration of the antenna base followed by frequent adjustment of the reception paths.
During transmission, the problem is more complex since it involves adjusting the transmission paths (after calibration of the antenna base) while being independent of the structure of the antenna base.